"Time and again, bacteria and other microbes have allowed animals to transcend their basic animalness and wheedle their way into ecological nooks and crannies that would be otherwise inaccessible; to settle into lifestyles that would be otherwise intolerable; to eat what they could not otherwise stomach; to succeed against their fundamental nature. And the most extreme examples of this mutually assured success can be found in the deep oceans, where some microbes supplement their hosts to such a degree that the animals can eat the most impoverished diets of all - nothing."
I Contain Multitudes: The Microbes Within Us and a Grander View of Life - Ed Yong

-Ed Yong in I Contain Multitudes (2016)